The purpose and intent of this project is to conduct tests, research, and experiments directed toward the use, improvement, and development of clinical procedures and instruments for measuring functions or properties relating to optics and physiology of the eyes. This has consisted primarily of subjective measurements of visibility and chromaticity thresholds, which provide our best estimate of the functional efficiency of the rods and cones in the retina. In cases of corneal, lens, or vitreous abnormality, transparency of the media is involved, but usually the sensitivity of the endorgans is measured as an index of the genetic, degenerative, toxic, or pathological condition of the retina.